KABUL -- Former Afghan President Hamid Karzai says the killing of Taliban leader Mullah Akhtar Mansur in a U.S. drone strike has damaged the prospects of a negotiated peace settlement with the militant group.

Karzai, in an interview with RFE/RL's Radio Mashaal in Kabul on June 2, also called the war in Afghanistan a "foreign problem” and called on countries such as Russia, Iran, and India to be involved in the peace process.

He said the May 21 drone strike that killed Mansur in the Balochistan Province of southwestern Pakistan "has hurt the peace process."

"If the intention was peace, then this shouldn’t have been done," Karzai said.

During the last years of his 2002-14 presidency, Karzai had a rocky relationship with the United States and was critical of U.S. air strikes, which he said were killing too many civilians rather than the militants they targeted.

Washington and Kabul hailed Mansur's death as a possible breakthrough in restarting stalled peace talks with the Taliban.

Mansur had refused to engage in a series of talks held in Islamabad and attended by the Quadrilateral Coordination Group (QCG), made up of officials from Afghanistan, Pakistan, the United States, and China.

The group has been trying to facilitate direct talks between the Afghan government and the Taliban since 2015.

Under Mansur's leadership, the Taliban made substantial military gains against Afghan security forces and carried out deadly bombings in Kabul.

Since Mansur’s death, the Afghan Taliban has announced that Mullah Haibatullah Akhundzada, a religious hard-liner, is the new Taliban leader.

In a recent audio recording, a voice purported to be Akhundzada's vowed in a recent audio recording that there will be no return to peace talks.

The drone strike that killed Mansur was the first known U.S. attack on a top Afghan Taliban leader on Pakistani soil.

The attack angered Islamabad, which has accused Washington of violating its territorial integrity.

"As it looks now and from all that I have heard in the statements from the Taliban, the government of Pakistan, others, it has hurt the peace process," Karzai said.

The ex-president also called for a regional solution to the conflict in Afghanistan.

He specifically called for Russia and neighboring Iran and India to be involved in any political settlement with the militants.

"If peace in Afghanistan was our own issue, a matter among Afghans, then why did the United States get involved or why did Pakistan and China engage in talks?" Karzai said. "Their involvement [in the peace efforts] proves that our problem exists outside and is foreign."

He added: "Since it is a foreign problem, there are foreigners that are powerful and strong and can have influence [on the talks]. Such actors are Russian, India and Iran -- these countries should also be included in the process so that we can have results."

Karzai has close ties with India, where he once studied and which he has visited often, including after stepping down as president in 2014.

India has been a key supporter of Kabul since the U.S. invasion in 2001, a stance that has led observers to point to the threat of a "proxy war" in Afghanistan between India and archrival Pakistan.

Karzai has also forged warm ties with one-time Afghan nemesis Moscow.

During his time in power, Karzai was keen to bolster ties with regional players like Russia to shore up security after the pullout of most NATO troops from Afghanistan in 2014.

Moscow has a vested interest in containing the Islamic State (IS) militant group and other extremists. IS and Taliban fighters have made advances in northern Afghanistan, near the border with the former Soviet republics of Central Asia. Moscow is also worried about the Afghan drug trade, which could worsen Russia's destructive heroin epidemic.

Russia has signaled its willingness to boost its involvement in Afghan security and provide weapons and training to Afghan forces.

In October, Russian President Vladimir Putin described the situation in Afghanistan as "genuinely close to critical" in an address to fellow Commonwealth of Independent States (CIS) leaders at a summit in Kazakhstan.

Putin warned of "terrorists of different stripes...gaining more influence and not hiding their plans for further expansion" and urged neighbors to "be ready to react in concert."

In the past year, a number of Afghan lawmakers and high-profile officials, including Afghan Vice President Abdul Rashid Dostum, a former warlord and Afghan Army general, have visited Russia to request helicopter gunships and heavy weapons.

But Moscow has so far been wary of increasing its role in Afghan affairs. The Soviet Union's calamitous 1979-89 military venture in Afghanistan killed or displaced millions of Afghans and sapped Moscow's precious political, military, and economic resources in the Soviet Union's dying decade.